Device for and method of controlling high frequency currents



Feb. 25; 1941. A, v, HAEFF 2,233,126

DEVICE FOR AND METHOD OF CONTROLLING HIGH FREQUENCY CURRENTS Original Filed Unit. 23, 1933 4 Sheets-Sheet 1 i l 1 i l i l l I ll 70 I INVENTOR /0 20 30 0 50 ANDREW V.HAEFF VOLTAGE V g g ATTO RN EY A. v. HAEFF 2.233.126

DEVICE FOR AND METHOD OF CONTROLLING HIGH FREQUENCY CURRENTS Feb. 25, 1941.

Original Filed Oct. 23. 1953 4 Sheets-Sheet 2 \NVENTOR ANDREW V. HAEFF ATTORNEY 13. llll IIII llllllllllllll II R k a a. E Mm w 2 mm Q E Q Q mm Q Q a 9mm Feb. 25, 1941. A v HAEFF 2,233,126

DEVICE FOR AND METHOD OF CONTROLLING HIGH FREQUENCY CURREN'IS Original Filed Oct. 23, 1933 4 Sheets-Sheet 3 ll Ir boa/mar INVENTOR ANDREW V. HAEFF ATTORNEY Feb. 25, 1941.- A. v. HAEFF DEVICEv FOR AND METHOD OF CONTROLLING HIGH FREQUENCY CURRENTS Original Filed Oct. 23, 1933 4 Sheets-Sheet 4 INVENTOR gm HAEFF ATTORNEY Qx mi L W1) IMWNIMIHIWIIWHIIHHHHH l Hh t lwl l l H i 9 5 5 2222;? v m Q 5 Ml HHHHHH- ,HH HHHH. ii &\

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H MEAN Patented Feb. 25, 1941 UNITED STATES PATENT OFFICE DEVICE FOR AND METHOD OF CONTROL- LING HIGH FREQUENCY CUBBENTS Andrew V. Haefl, East Orange, N- 8., assignor to Radio corporation of America, a corporation of Delaware 22 Claims. (01. 250-27) This invention is a division of my United States Patent No. 2,064,469, granted December 15, 1936,

on an application Serial No. 694,794, filed ctober 23, 1933, and relates broadly to the art of generating, controlling and measuring high frequency electric waves and is particularly useful with waves of such extremely high frequencies that they cannot be effectively controlled with vacuum tubes of conventional'types now in general use because of the inter-electrode capacity and low electron velocity characteristics of conventional tubes.

A broad object of the invention is to provide apparatus for and methods of efllciently generatlng, controlling and measuring extremely high frequency electric waves.

Another object is to increase the sensitivity and stability of apparatus for generating, controlling and measuring extremely high frequency waves.

Most conventional vacuum tubes for use in connection with radio frequency currents employ a grid or grids placed in an electron stream created between a cathode and an anode mounted in an evacuated container; by applying an alternating potential between the cathode and grid, the rate of flow of the electrons to the anode is varied in synchronism with the alternating potential applied to the grid. Tubes of this type have definite upper frequency limitations because at extremely high frequencies the inherent interelectrode capacity effectively short circuits those elements and prevents the building up of any substantial potential difference between the cathode and grid, and, further, because at extremely'high frequencies the grid potential reverses in a time less than that required for electrons to travel from the cathode to the grid. For these reasons, tubes of the conventional type described become inoperative, for all practical purposes, at extremely high frequencies.

In accordance with the present invention, the aforementioned difiiculties encountered with conventional tubes are avoided by using as a con- 45 trolling device a modification of the well known cathode ray oscillograph, in which an electron stream is deflected laterally and thereby caused to impinge to a varying extent on one or more suitably positioned anodes. This method differs fundamentally from the method of operation of the conventional vacuum tubes previously mentioned since in the latter, the rate of flow of electrons in a stream is varied instead of the electron stream being deflected laterally.

The theory of operation of my invention and various forms of apparatus in which it can be employed will be explained in detail with reference to the drawings, in which:

Fig. 1 is a schematic diagram of a radio receiving circuit employing an electronic tube of the general type to which this invention relates;

Fig. 2 is a schematic diagram illustrating the deflection 'of the electron stream in the tube of Fig. 1 when the period of the applied alternating current is long as compared to the time required for the electrons to travel through the tube;

Fig. 3 is a schematic diagram illustrating the deflection of the electrons in the tube of Fig. 1 when the period of the applied alternating current is short as compared to the time required for electrons to travel through the tube;

Fig. 4 is a schematic diagram illustrating the deflection of the electron stream in the tube of Fig. 1 when the tube is operated'in such a manner as to produce travelling waves on the control electrodes of the tube, which waves travel at the same speed as the electrons in the electron stream;

Fig. 5 is a graph illustrating the sensitivity characteristics of a tube operating in the manner illustrated in Fig. 4 when the velocity of the electron stream is varied with respect to the speed of propagation of the controlling waves along the control electrodes; v

Fig. 6 is a view partly in section of one form of vacuum tube in accordance with my invention;

plane at right angles to the plane of Fig. 6;

Fig. 8 is a cross-section of the vacuum tube shown in Figs. 6 and 7 taken in the plane VIII-VIII of Fig. '7;

Fig. 9 is a schematic diagram of a detecting or rectifying circuit employing the vacuum tube shown in Figs. 6, '7 and 8;

Fig. 10 is a detail view showing a modified form of anode structure for tubes of the type shown in Figs. 6, '7, 8 and 9;

Fig. 11 is a schematic diagram of an oscillograph tube constructed in accordance with the invention;

Fig. 12 is a schematic diagram of an oscillator circuit employing a tube of the type shown in Figs. 6, '7 and 8;

Fig. 13 is a longitudinal sectional view of an alternative tube construction to that shown in Figs. 6, 7 and 8;

Fi 14 is a sectional view of the same tube Fig '7 is a view of the same tube taken in a shown in Fig. 13 taken in the longitudinal plane at right angles to the plane of Fig. 13; and

Fig. 15 is a schematic diagram of a detecting or rectifying circuit employing the tube of the type illustrated in Figs. 13 and 14.

Referring to Fig. 1, there is shown an electronic tube, designated generally at I, comprising an evacuated receptacle 2, containing a cathode 3, a pair of anodes 4 and 5, and a pair of control electrodes 6 and l. The cathode 3 may be of any suitable type adapted to be heated and having a coating of high electron emitting characteristics whereby it emits large quantities of electrons. A grid 8, which may be of various shapes, is positioned adjacent the cathode 3 and maintained at positive potential with respect to the cathode by means of a battery or other suitable source of potential 9. Because of its potential, the grid 8 attracts electrons from the cathode 3, many of which electrons impinge upon the grid and produce no useful result. However, some of the electrons pass through an aperture I!) in the center of the grid 8 and travel longitudinally through the tube to the anodes 6 and 5, these electrons constituting an electron stream II. It is to be understood that cathodes in combination with focusing devices for producing and directing a stream of electrons, are old, and that various particular forms of apparatus have been developed for this purpose, some of which may be substituted for the particular apparatus shown in Fig. 1. In the type of apparatus disclosed, the electrons in the stream ll travel at substantially constant velocity from the grid 8 to the anodes 4 and 5 since those elements are maintained at substantially the same potential. By properly designing the electron emitting and concentrating apparatus, the electron stream H may be confined to a relatively small cross sectional area.

The control electrodes 6 and 1 are positioned parallel to each other on opposite sides of the electron stream II and are adapted to be connected at one end to a suitable source of high frequency oscillations such as an antenna i2. The antenna is preferably connected to ground through impedance elements I 2a to stabilize the average potentials of the electrodes 6 and "I.

The anodes 4 and 5 are preferably of somewhat larger areas than the cross sectional dimensions of the electron stream II and are positioned close together so that under normal conditions the stream ll impinges on both anodes. In the particular circuit shown, the anode 5 is connected directly by conductor l3 to the grid 8 and is also connected to the cathode Id of a conventional three-electrode amplifying tube Ma. The anode 4 of tube l is connected through a condenser IE to the grid l6 of the three-electrode tube Ida and a high impedance element I 1 is connected between the anode 4 and the conductor I3. A grid leak i8 and a 0 battery l9 may be connected in series between the cathode l4 and grid I 6 of the three-electrode tube I do to properly bias the grid it. A telephone |9a may be connected in series with a B battery 20 between the cathode l4 and anode M of the three-electrode tube to produce an audible signal in response to a modulated wave detected by the tube l and amplified by the tube Ma.

When no potentials are applied to the control electrodes 6 and 'l, the electron stream ll impinges upon both anodes 4 and 5, setting up direct currents therein which flow through the conductor l3 back to the cathode 3. Since the condenser l5 offers substantially infinite impedance to direct currents, the potential of the grid is is constant, being determined by the battery l9, and the current flowing in the output circuit of the three-electrode tube Ma and the'telephone lfla is constant.

When the antenna I2 is exposed to radio waves, currents of the frequency of the radio waves are generated in the antenna and applied to the control electrodes 6 and 1. If the waves are of relatively low frequency, the potential of all parts of each electrode 6 and 1 will be substantially the same at any instant but during half of each cycle one electrode will be positive and the other negative, whereas during the other half of each cycle the polarities of each electrode will be reversed. When the control electrodes 6 and 1 are at opposite potentials, an electric field exists between them which exerts a force on each electron in the stream ll, tending to shift the electrons laterally from their normal longitudinal path of travel. Thus during that half of each cycle when the electrode 6 is positive and the electrode 1 is negative, the stream II will be deflected upwardly to impinge to a greater extent on the anode 4 and during the intervening half cycles when the electrode 1 is positive with respect to the electrode 8, the stream II will be deflected downwardly so that it impinges to a lesser extent on the anode 4. It follows that the number of electrons impinging on anode 4 will be varied in synchronism with the radio wave. Since the electronic current to anode 4 is made to pass through the impedance II, the voltage across ,this impedance will vary with the frequency of the radio wave. However, if the impedance H is of such a nature that it ofiers low impedance for the radio frequency, the radio frequency voltage across impedance I! will be small. If the radio wave is modulated with a signal wave, such as an audio frequency current, its amplitude will vary in accordance with the signal. Now, if .the stream I i is directed on the anodes 4 and 5 in such a manner that the average current to anode 4 varies with the amplitude of the radio wave on the controlling elements 6 and 1, then the average potential across impedance I! will vary with signal frequency, the element l7 offering high impedance for signal frequency. The varying potential across element I1 is applied through the condenser i 5 to the grid I 6 of the three-electrode amplifying tube Ma and correspondingly varies the current in the output circuit of the tube Ma to reproduce the audio signal in the telephone Illa.

Results theoretically can be obtained at any frequency, but at high frequency the sensitivity is extremely low so as to make this device impractical. When the frequency of the radio waves applied to the electrodes 6 and l is so low that the time of a complete cycle is large as compared with the time required for an electron in the stream H to travel the length of the electrodes 6 and 1, electrons, while travelling between the control electrodes 6 and I, will be urged in a single lateral direction (either toward the electrode 6 or toward the electrode 1) throughout its path. Hence the path of the electrons will be substantially parabolic and the extent of lateral deflection will increase rapidly with the length of the electron stream and the length of the electrodes 6 and l. readily apparent, therefore, that the sensitivity of a tube of this type depends to a large extent It will be aaaa'rao upon the length of the electron stream and of the electrodes C and I.

Fig. 2 shows clearly the deflection oi the electron stream ll under the conditions described. at an instantwhen the electrode 8 is positive and the electrode I is negative. Itwiii be ob served that the electron stream is diverted toward the anode l. Oi course. during the succeeding half cycle the conditions will be reversed and the electron stream will be diverted toward anode 5.

Now assume that the velocity of the electrons in the stream ll remains the same as before (being determined by the potential diilerence between the cathode 3 and the grid 8) but that thefrequency of the radio waves applied to the antenna I2 is enormously increased so that the period of a single cycle of the radio frequency currents applied to electrodes 8 and I is substantially less than the time required for an electron to travel from the grid 8 to the anodes 4 and three-electrode amplifying tube. This condition is illustrated in Fig. 3. It will be observed from this figure that some deviation of the electron stream ii is produced'but thatit is very slight andis no greater adjacent the anodes I and 5 than at a point remote therefrom. Under the conditions outlined, the circuit of Fig. 1 would be substantially inoperative to produce any useful result.

It has been assumed in the discussion in the preceding paragraph that all portions of each electrode 6 and I would be of substantially the same potential at any instant. Such a condition would be difficult, if not impossible, to attain because, at the extremely high frequencies assumed, the wavelength of the radio frequency currents applied to the electrodes 6 and 1 might be comparable to the actual length of the electrodes so that at a given instant one portion of each electrode might have one polarity and another portion 'anoth'er polarity. Moreover,

'unless the velocity of the wave along the electrodes 6 and I were made equal to the velocity of the electrons in the stream II. the result would be substantially the same as though all portions of each electrode were assumed to be at the same potential at any given instant. Furthermore, if the electrodes 6 and I constitutements and is no greater than in a device with deflecting elements of such length that electrons traverse them in less than the period of one-half cycle. However, such a device would be impracticable because of its lack of sensitivity. In other words, to produce appreciable deflectube may be calculated from the formula where L is the length of the controlling elements, V is the speed of the electrons in the stream ii and T is the period of oscillation of the wave applied to the electrodes 6 and I.

I In accordance with the present invention, it is possible to etfectively use controlling elements of length much greater than thereby greatly increasing the sensitivity of the device. The invention is based on the principle that if the speed of the electrons in the stream is made equal to the velocity of propagation of the electromagnetic waves along the control electrodes, then electrons which travel with the crest of the wave along the electrodes will be subject to a force acting continuously in the same direction throughout the whole length of the controlling element in spite of the fact that the time of travel may be many times the period of oscillation. Thus, referring to Fig. 4, assume that the waves generated in the antenna l2 and applied to electrodes 6 and I are of such high frequency that the potential distributed along the electrode 6 at .a given instant is as represented by the curve 22 and the potential along the electrode 1 is as represented by the curve 22. Assume further that the velocity of propagation of the wave indicated by curves 22 and 23 along the electrodes Ii and I is substantially less than the velocity of light, (means for and methods of reducing the velocity of the waves will be described later) and that the velocity of the electrons in the stream II is made equal to the velocity of the electromagnetic wave along electrodes 6 and I by adjusting the potential 9 between the cathode 3 and the grid 8. Under the conditions outlined, at any given instant certain longitudinal points along the electrodes y 6 and I will be positive and negative, respectively, and at those points electrons in the stream II will be deflected upwardly, as shown at 24 and 25. At the same time intermediate portions of the electrodes 8 and I will be negative and positive, respectively, and electrons in the stream Ii at this point will be deflected downwardly, as shown at 25. The wave, however, is moving from left to right along the electrodes at the same speed that the electrons in stream II are moving'from left to right so that any given electrons are urged laterally in the same direction (either toward the electrode 6 or the electrode 1) throughout their travel between the electrodes. and a cumulative deflection of the electrons is produced substantially as was described in connection with Fig. 2. Therefore, the amplitude of lateral deflection of the elec trodes, may attain substantial proportions and cause the electron stream to be deflected to a substantial extent from one to the other of the anodes l and 5.

Although in a tube operating in accordance with Figs. 1 and 4 maximum sensitivity is obtained when the speed of the electrons in the stream ll exactly equals thelongitudinal speed of propagation of the exciting wave on electrodes 6 and I, it is not essential that the speeds be exactly the same in order that the device be operative. The relation between sensitivity and the relative speeds of the electrons and the electromagnetic waves is illustrated graphically in Fig. 5 in which the ordinate represents sensitivity and the abscissa the potential difference between the grid 8 and the cathode 3 of a tube actually tested. In this test the velocity of propagation of the waves along the electrodes 6 and I remained constant, being determined by the construction of the electrodes, whereas the velocity of the electrons in the stream ll varied with the potential between cathode 3 and the grid 8. It will be observed from Fig. 5 that the tube is not at all critical with respect to electron velocity but is operative over a relatively wide range of grid potential (grid potential referring to the potential difference between the cathode 3 and the grid 8). The sharpness of this curve depends upon the length of the controlling electrodes, which may be many wave-lengths long, electrically, the sharpness being more pronounced the greater the length of the electrodes expressed in terms of wavelengths.

In Fig. 1 the electrodes 6 and I are shown as open-ended conductors so that if the antenna 12 were excited with extremely high frequency radio waves, these waves would be reflected from the ends of the electrodes 6 and 1 to produce the effect of standing waves. However, this would not in any way interfere with the operation of the device as described because a standing wave is really the resultant of two substantially equal waves travelling in opposite directions. The component of the standing waves travelling from right to left along the electrodes 6 and E would produce substantially zero effect upon the electrons in stream I I for the reasons outlined in connection with Fig. 3, i. e., each electron in the stream I I would be acted upon in rapid succession by succeeding waves, each tending to shift it in the opposite direction so that the net result would be negligible. On the other hand, the component of the standing waves travelling from left to right along the conductors would cumulatively afiect the electrons in the stream II for the reasons set forth. The use of standing waves is very advantageous since the radio frequency voltage on electrodes 6 and I can be built up considerably if the circuit, of which elements 5 and I are a part, is tuned to the frequency of the received radio signal.

It will be apparent from the discussion so far that the usefulness of my invention is dependent upon practical methods of making the velocity of the electrons in the stream ll equal to the velocity of propagation of electromagnetic waves along the electrodes 3 and 7. As previously stated, the velocity of electromagnetic waves along ordinary straight conductcrs is substantially equal to the velocity of light and it is very diflicult, if not impossible, to produce an electron stream of such high velocity. It follows that the velocity of propagation of the electromagnetic waves along the electrodes 6 and I must be reduced substantially below the velocity of light. This may be done in a number of ways. The most obvious method and the one which I prefer to employ is to increase the actual lengths of the electrodes 6 and 1 relative to their dimensions parallel to the electron stream ll by coiling or doubling back the conductors constituting the electrodes 6 and 1 so that the total length of conductor in each electrode is much greater than the distance from end to end of the electrode parallel to the electron stream. Coiling the conductor in the form oi a helix has the further advantage that it increases the inductance of the conductor, which in itself tends to reduce the velocity of propagation.

Another method of reducing the velocity of propagation would be to employ as the electrodes 3 and 1 conductors coated with magnetic material to greatly increase the inductance of the conductors. It is doubtful, however, that this method is practicable with present known magnetic materials because of their low permeabilities and high hysteresis and eddy current losses at extremely high radio frequencies.

The construction of an actual tube for use in circuits similar to that shown in Fig. 1 is illustrated in Figs. 6, 7 and 8. This tube comprises an evacuated receptacle 30, in one end of which there is supported a straight filamentary cathode 3! at right angles to the longitudinal axis of the tube. Thus it is shown supported between a pair of spring elements 32, which in turn are supported from a glass standard 36. The spring elements 32, in addition to serving as supports for the cathode 3|, supply current thereto and are connected to lead-in conductors 34 sealed through the wall of the receptacle 30. The cathode 3! is mounted within a U-shaped shield 35 supported from the I glass standard 36, which extends substantially the length of the tube. The shield 35 is connected through a separate leadin conductor 33 to the exterior of the receptacle 30 and in operation is maintained at a negative potential with respect to the cathode 3| to tend to reflect and focus electrons from the cathode toward the opposite end of the tube. Positioned within the open end of the U-shaped shield 35 is another slightly smaller semi-cylindrical element 37, the open end of which faces in the same direction as the shield 35. This element 31 is attached to an open-ended member 38 of substantially rectangular shape, which in turn is supv ported from the standard 36. Still another element 39 is positioned concentrically within the element 31 and also supported from the standard 36. Element 39, like element 31, is closed on all lateral sides and constitutes an open-ended box of rectangular shape. The elements 37 and 39 constitute the equivalent of the grid structure 8 in Fig. 1 and are preferably provided with open mesh grid structures 40 at their ends adjacent the cathode 3|. Elements 3! and 39 are connected through separate lead-in conductors 31a and 39a to the exterior of the tube and in operation are maintained at positive potentials with respect to the cathode 3| under which conditions they accelerate electrons emitted by the cathode 3| and concentrate them in an electronic stream of substantially oblong cross section toward the opposite end of the tube. It isto be understood that structures for producing beams of electrons are broadly old and that other structures than those described may be employed.

The glass standard 36, as previously mentioned, is continuous and extends longitudinally of the tube on opposite sides of the electron stream, the latter being preferably directed along the axis of the tube. The mid-portions of the standard 36 are enlarged through that portion of their length juxtaposed to the electron stream issuing from the open-ended element 39 and support control electrodes which are constituted by wires 42 and 43 wound about the juxtaposed portions of the standard 38 in the form of helices. Opposite ends of each helix 42 and 43 arev'connected to separate lead-in conductors- 44, 45, 45 and 41, respectively.

A pair of anodes 48 and 49 are positioned in the end of the tube opposite to the cathode 3| and beyond the ends of the helices 42 and 43. As shown in Figs. 6 and 7, each anode 48 and 49 comprises a fiat plate 59 and 5|, respectively, positioned at anangleto the longitudinal axis of the tube and secured to base plates 53 and 54, positioned at right angles to the plates 59 and 5|, respectively. The plates 53 and 54 are supported from the standard 36, as shown, and are connected to separate lead-in conductors 55 and 56. For the purpose of absorbing secondary electrons emitted from the plates 59 and 5|, respectively, they are surrounded by open-ended shields 51 and 58, respectively, which are of rectangular cross section and are supported from the standard 38 and connected to individual leadin wires 59 and 89, respectively.

The operation of the tube just described as a detector is illustrated in Fig. 9. Referring to Fig. 9, the cathode 3| is shown connected to a source of heating current GI and the shield 35 is connected through a resistance element 82 to one end of the cathode 3|. Certain of the electrons impinging upon the shield from the cathode 3| tend to raise the shield 35 to a negative potential above the cathode 5|, thereby producing a potential across the resistance 62. By properly proportioning resistance 62, the potential of the shield 35 may be regulated within limits. The gridelements 31 and 39 are maintained at positive potentials with respect to the cathode 3| by any suitable source of direct current which has been indicated as a rectifier in Fig. 9. The element 39 is maintained at a higher potential than the element 31 by connecting element 39 directly to the positive terminal of the rectifier and connecting the element 31 to a tap.

83 of a potentiometer shunted across the rectifier. By suitably adjusting the potentiometer, the relative potentials of the elements 31 and 39 may be regulated to produce potential gradients between the cathode 3| and element 31 and between element 31 and element 39 or proper magnitudes to efficiently concentrate a stream of electrons derived from the cathode 3|. The velocity of the electrons in the stream may also be regulated within certain limits by varying the potential of the element 39 with respect to the cathode 3|; It has been found convenient to maintain the last grid element 39 through which the electrons pass at ground potential by grounding the positive terminal of the rectifier as indicated at 65.

The anodes 48 and 49 of the tube are connected substantially in the same manner previously described in connection with Fig. 1. Thus the anode 48 is connected through a condenser 68 to the grid 61 of a three-electrode amplifying tube 88 and the anode 49 is connected through a battery 89 and condenser 19 to the cathode 1| of the three-electrode amplifying tube 68. The anode 12 of tube 8 8 is connected through a telephone 13 and a B battery 14 to the cathode 1|. A grid leak 81a. is connected in shunt to the cathode 1| and grid 81 to maintain a suitably V biasing potential upon the grid 81. A high impedancereturn path to ground for electrons impinging on anode 49 is provided through a resistance 15, and an impedance 18 provides a impedance of elements 11 and 18, shields 51 and 58 are maintained negative with respect to their associated plates 50 and 5| so that a field is created between each plate and its associated shield tending to' return secondary electrons'emitted from each plate back to that plate. The main purpose of this type of anode structure is to prevent the secondary electrons emitted from elements 51 and 48 from impinging upon elements 58 and 49, and vice versa. This has been found desirable since the emission of secondary electrons tends to decrease the effect of deflection of the primary stream of electrons unless the secondary electrons are properly taken care of.

The helices 42 and 43, respectively, constituting the control electrodes for deflecting the electron stream within the tube, are connected in series in the respective sides of a Iecher circuit, one end of which is terminated by the antenna conductor 19 and the other end by a condenser 80, which is of sufficient capacity to act as a short circuit at the frequency for which the Lecher circuit is tuned and reflect the waves back along the circuit. The two ends of the Lecher circuit beyond the condenser 80 are connected across a potentiometer 8|, the terminals of which are connected to a battery 82 and the mid point of which is connected to ground through a resistance 82a. By suitable adjustment of the taps on potentiometer 8|, constant direct current potentials may be superimposed on the helices 42 and 43 for biasing the electron stream into a desired normal position. When the device is used as a detector, the relative constant potentials of helices 42 and 43 are so adjusted as to cause substantially the entire electron stream to impinge on plate 5| and shield 58 of anode 49.

When the antenna 19 is excited, standing waves are produced in the Lecher system, including the helices 42 and 43, and the distance between crests of waves on the helices is determined by the diameter and pitch of the helices. Likewise the velocity of propagation of the waves longitudinally along the helices is determined by their pitch and diameter-and by making these of suitable values the velocity of the waves may be reduced substantially below the velocity of light. The speed of electrons in the beam projected through the tube is then adiusted to substantially equal the speed of propagation of the waves along the helices by adjusting the potentials on the electron accelerating electrodes 31 and 39. Under these conditions the waves on the two helices 42 and 43, which are 180 out of phase with each other, produce a voltage gradient in the space traversed by the electron stream in a direction transverse to the direction of the stream, thereby periodically deflecting it. As a result of the deflection of the electron stream, the electronic currents flowing to the anodes 48 and 49 pulsate at the same frequency as the waves on the helices. The average current to either anode 48 or "will vary with the'amplitude of the radio frequency wave provided the electron stream is biased (by suitably adjusting the potentiometer 8|) so that the change of plate current is not linear with the deflection.

Thus, if the beam is biased by adjustment or potentiometer 8| so that the upper edge of the beam normally coincides with the lower edge of anode 48, then when no radio frequency signal is applied, substantially the entire current in the electron beam flows to anode 49 and none to anode 48. However, when the beam is periodically deflected, part of the total electronic current in the beam will flow to anode 48 and the value of the latter current will depend upon the amplitude of periodic deflection. The best ad- .iustments for maximum and distortionless detection depend upon the cross section of the beam and the structure of the anodes. The varying electronic current applied to anode 48 passes through the high impedance element 16 to ground and thence back to the cathode of the tube through the rectifier 64. The potential across the impedance l6 varies with the average current therethrough, which in turn varies with the amplitude of the high frequency wave on the helices. This potential is applied through condenser 66 to the grid 61 of the amplifying tube 68, in which it is amplified and applied to the telephone 13. If the high frequency wave is modulated with a wave of audio frequency, the amplitude of the high frequency wave will vary at audio frequency and hence the current in the telephone '13 will vary at the audio frequency.

It is to be understood that it is not absolutely necessary to the operation of the circuit of Fig. 9 that the transmission line in which the helices 42 and 43 are inserted be terminated in a manner to produce reflection (as by means of the condenser 80). An absorption circuit having an impedance equal to the surge impedance 01' the line may be substituted for the condenser 80, in which case there will be no reflection and no standing waves produced. However, when the waves are reflected, their amplitude is increased, thereby making the circuit more eflicient.

A modified form of anode structure showing a method of reducing the capacity between the anodes is shown in Fig. 10, in which the anodes 83a and 8411 are positioned substantially at the same point longitudinally of the tube but are separated by an electrode 81 which is maintained at a negative potential with respect to the anodes 83a and 840. by connecting it through a battery 88 to ground. An impedance 89 is connected between anodes 83a. and 840. at the voltage node of the timed Lecher system. The electrode 81 being negatively charged, tends to disperse the electron stream laterally toward the anodes 83a and 84a so that as the beam is deflected laterally it impinges to a greater or less extent on the two anodes. This method of reducing the capacity between the anodes is advantageous in that it makes the same tube suitable for a wide range of frequencies.

My invention is also adaptable for use in cathode ray oscillographs, in which the electron stream instead of being directed upon anodes, as previously described herein, is projected upon a fluorescent screen. Thedeflection of the beam in one plane is obtained by a pair of opposite helices I and I III, respectively, in Fig. 11, and in the opposite plane by a pair of helices I02 and I03, respectively. All of these helices are so proportioned as to pitch and diameter that the speed of propagation of electromagnetic waves therealong is substantially the same as the speed of propagation of the charged particles in the electron stream so that travelling waves on any or all of the diflerent helices produce cumulative eflectson the electrons in the stream. In operation one pair of opposite helices would be connected to a source of oscillations to be measured or observed and the other pair of helices connected to a control wave of predetermined frequency in accordance with present accepted oscillograph practice.

There is shown in Fig. 12 an oscillator circuit utilizing a tube in accordance with my invention. This circuit utilizes a tube 90 of the same type as the tube of Fig. 9, in which the control electrodes or helices 42 and 43 are included in a Lecher circuit 9| and in which the anodes 83 and 84 of the tube are also connected into the Lecher circuit at suitable points. With this arrangement only a small proportion of the output potential developed in the anodes 83 and 84 will be required to maintain oscillations in the Lecher system 8| so that the excess power may be delivered to an output circuit as shown.

Obviously various modifications may be made in the circuits shown in Figs. 9 and 12. Thus by employing in the circuit of Fig. 9 a tube of the type shown in Fig. 12 and feeding back a portion of the radio frequency current in the output circuit of the tube, into the antenna circuit in the manner disclosed in Fig. 12, a regenerative detector may be obtained.

As an example of the various forms which electrical discharge devices in accordance with my invention may take, a special type of tube is illustrated in Figs. 13 and 14. -This tube differs from the tube shown ln Figs. 6 and 7 in that the cathode lIli instead of being straight is substantially circular and positioned concentrically with respect to the axis of the tube. The shield H6 surrounding the cathode H is in the form of an annular trough II'I joined to a cylindrical member 8 and the electron accelerating and concentrating elements H9 and I constitute annular troughs having open grid structures HI and I22 at their rear ends which are concentric with and positioned in front of the circular cathode II5. This cathode and electron accelerating and concentrating structure produce a hollow electron beam I23 of circular cross -section which is projected the length of the tube onto a pair of anodes I24 and I25, anode I25 being in the shape of a disc and anode I24 in the shape of a washer positioned concentrically with respect to anode I25. The anodes are so dimensioned that the hollow electron beam I23 normally impinges upon the circular division line between the two anodes. The anode I25 may be positioned back of the anode I24 to reduce the inter-anode capacity for reasons previously described.

The control electrode preferably consists of a single helix I26 positioned within the electron beam I23, the ends of the helix being brought out to the exterior of the tube through lead-in conductors I21 and I28, as shown in Fig. 14. A metallic cylinder I29 is positioned concentrically about the helix I26 and is of substantially larger diameter so that it surrounds and encloses a portion of the electron stream. The cylinder I29 is connected to the exterior through lead-in conductor I30 and serves 1) to prevent accumulation of charges on the glass walls of the tube; (2) to provide means for establishing a constant radial electric fleld between the helix and the cylinder to bias the stream whereby it impinges in desired degree upon the two anodes I24 and I25, and (3) to shield the helix from external fields so that the sensitivity of the device does not depend upon the proximity of external bodies.

A circuit for use with the tube described is shown in Fig. 15. It will be observed that the cathode is heated by an independent source of direct current connected to opposite ends thereof and that the anodes I24 and I25 are maintained at average potentials positive with respect to the cathode by means of a source of potential indicated as a rectifier. The anode I24 is shown connected directly to the positive terminal of the rectifier through a compensating battery I3Ia and the anode I25 is connected to the positive terminal of the rectifier through an impedance element I3 I The normal average electronic current flowing to anode I25 produces a potential drop in the impedance I3I which would normally maintain this anode at a different potential from anode I24 were not the battery I3Ia. provided to compensate therefor. The electron accelerating and concentrating elements II9 and I20, respectively, are maintained at suitable positive potentials with respect to the cathode I I by connecting them to taps on a potentiometer I32 connected across the rectifier, and the cylinder I29 is shown connected to the final electron concentrating element I20 to maintain them at the same potential and eliminate any potential gradient in that portion of the electron stream between element I20 and cylinder I29.. A radial potential gradient for biasing the electron beam into a desired normal position with respect to the anodes I24 and I25 is provided by means of a source of variable potential I33 connected between the cylinder I29 and the helix I26.

The control electrode constitutedby helix I26 is energized from any suitable source of potential by connecting the ends of the helix thereacross. In Fig. 15 the source of potential is shown as an antenna I34 connected to a pair of Lecher conductors I35, the latter being terminated by a condenser I36 adjustable therealong for producing standing waves in the manner that has been previously described. The ends of the helix I26 are preferably connected across two Lecher conductors I35 at such points as to produce a maximum excitation of the control electrode.

Because of the manner in which the helix I26 and cylinder I29 are connected through the po tentiometer I32 to the rectifier and of the fact that the anodes are connected to the positive terminal of the rectifier, the anodes are maintained at an average positive potential with respect to the helix I26 and cylinder I29 so that'secondary electrons emitted from the anodes return to the anodes. Furthermore, due to the potential gradient existing between the helix I26, cylinder I29 and anodes, the primary electrons in the beam are accelerated during the last part of their travel to the anodes. In order to make maximum use of the deflecting effect of the electromagnetic waves on the helix, the velocity of the waves on the right end portion of the helix isincreased to correspond with the increased speed of the electrons in the adjacent portion of the beam by suitably increasing the pitch of the helix at the end. By this means the velocity of the electromagnetic waves along the helix is approximately equal at any point to the velocity of the electrons in the portion of the stream adjacent that point although this velocity is not constant at all points along thehelix. when the device is in opera on the forces exerted on the beam, due to stan g' or travelling electromagnetic waves on thehelix, are directed radially so that the waves on the helix produce periodic contractions and expansions of the diameter of the stream,

which in turn produces periodic variations in the currents flowing to the anodes. The tube can be used as a detector, amplifier or oscillator by employing it in circuits similar to those disclosed in Figs. 9, and 11.

Having thus described my invention, what I claim is: 1

1. In an electrical discharge device, means for projecting a hollow beam of charged particles, means responsive to variations in diameter of said hollow beam, and means for propagating an electromagnetic wave longitudinally within said hollow beam at at least approximately the same velocity as the velocity of the charged particles in the beam, whereby the charged particles in the beam are cumulatively laterally deflected by an electromagnetic wave travelling along said electromagnetic wave propagating means.

2. In an electrical discharge device, means for projecting a hollow beam of charged particles, means responsive to variations in diameter of said hollow beam, and means for propagating an electromagnetic wave longitudinally within said hollow beam at at least approximately the same velocity as the velocity of the charged particles in the beam, whereby the charged particles in the beam are cumulatively laterally deflected by an electromagnetic wave travelling along said electromagnetic wave propagating means, and a tubular conductive shield positioned about a portion of said hollow beam surrounding said electromagnetic wave propagating means.

3. In an electrical discharge device, means for projecting a hollow beam of charged particles, means responsive to variations in diameter of said hollow beam, and means for propagating an electromagnetic wave longitudinally within said hollow beam at at least approximately the same velocity as the velocity of the charged particles in the beam, whereby the charged particles in the beam are cumulatively laterally deflected by an electromagnetic'wave travelling along said electromagnetic wave propagating means, said means for propagating an electromagnetic wave comprising a helical conductor.

4. In an electrical discharge device, means for projecting a hollow beam of charged particles, means responsive to variations in diameter of said hollow beam, and means for propagating an electromagnetic Wave longitudinally within said hollow beam at at least approximately the same velocity as the velocity of the charged particles in the beam, whereby the charged particles in the beam are cumulatively laterally deflected by an electromagnetic wave travelling along said electromagnetic wave propagating means, said means responsive to variation in diameter of said hollow beam comprising a central anode and an annular anode surrounding said central anode, said anodes being substantially perpendicular to the axis of said hollow beam and in concentric relation therewith.

5. In combination, a conductive target of annular shape, means for emitting and projecting a hollow stream of charged particles at a predetermined initial velocity toward said target, the axis of said hollow stream being concentric with respect to said target, a conductive helix positioned within said hollow beam and concentric with respect thereto, means for applying an elecsaid stream adjacent the anode end of said helix are accelerated, and the anode end of said helix being of progressively increasing pitch to correspondingly increase the longitudinal velocity of propagation of electromagnetic waves therealong, whereby successive portions of an electromagnetic wave propagated along said helix cumulatively radially deflect charged particles in said stream in the same radial direction during a substantial portion of their longitudinal-travel and causes them to impinge. in varying degree on said target, and means connected to said target responsive to variations in the number of charged particles impinging on the target. 6. In combination, a conductive target of annular shape, means for emitting and projecting a hollow stream of charged particles at a. predetermined initial velocity toward said target, the axis of said hollow stream beiing concentric with respect to said target, a conductive helix positioned within said hollow beam and concentric with respect thereto, means for applying an electromagnetic wave to said helix, the pitch of the front end of said helix being such as to cause electromagnetic waves applied to said helix to travel therealong at a longitudinal velocity substantially equal to the velocity of particles in said stream, a cylindrical shield surrounding at least a portion of said helix and electron stream, means for applying a constant biasing potential between said helix and shield for adjusting the average diameter of said beam, means for maintaining said anode positive with respect to said helix and cylindrical shield whereby electrons in said stream adjacent the anode end of said helix are accelerated, and means connected to said target responsive to variations in the number of charged particles impinging on the target.

' 7. In an electrical discharge device, means for projecting a hollow annular cylindrical beam of charged particles, means responsive to variations in diameter of said hollow cylindrical beam, and means for propagating an electromagnetic wave longitudinally within said hollow beam at at least approximately the same velocity as the velocity of the charged particles in the beam, whereby the charged particles in the beam are cumulatively laterally deflected by an electromagnetic wave travelling along said electromagnetic wave propagating means, said means for propagating an electromagnetic wave comprising a helical conductor.

8. In an electrical discharge device, means for projecting a hollow cylindrical beam of charged particles, means responsive to variations in diameter of said hollow cylindrical beam, and means for propagating an electromagnetic wave longitudinally within said hollow cylindrical beam at at least approximately the same velocity as the velocity of the charged particles in the beam, whereby the charged particles in the beam are cumulatively laterally deflected by an electromagnetic wave travelling along said electromagover a substantial portion of the length drical beam of electrons, and

netic wave propagating means, said means responsive to variation in diameter of' said hollow cylindrical beam'comprising a central anode and an annular anode surrounding said central anode, said anodes being substantially perpendicular to 5 the axis of said hollow beam and in concentric relation therewith.

9. In an electrical discharge device, means for producing and projecting a substantially cylin- I drical hollow beam of electrons, means responsive to variations inoverall diameter of said cylindrical beam, and means within said cylindrical beam and adapted to have varying potentials applied thereto for changing the overall diameter thereof.

10. In an electrical discharge device, means for producing andprojecting a substantially cylindrical. hollow beam of electrons, means responsive to variations in overall diameter of said cylindrical beam, means within said cylindrical beam 20 and adapted to have varying potentials applied thereto for changing the overall and a tubular conductive shield a portion of said hollow beam.

11. In apparatus of .the character described, a 25 ring shaped cathode, means for deriving and pm- Jecting therefrom a hollow substantially cylindrical beam of electrons, and means for varying the outside diameter of said beam of electrons in accordance with varying potentials applied to said means. v

12. In an electrical discharge device, means for producing and projecting a substantially cylintrical hollow beam of electrons, a pair of anodes adapted to intercept varying amounts of electrons in accordance with variations in overall diameter of said cylindrical beam, and means within and extending over a substantial portion of the length of said cylindrical beam and adapted to have varyingpotentials applied thereto for changing the overall diameter thereof.

13. In apparatus of the character described, a ring shaped cathode, means for deriving and projecting therefrom a hollow, substantially cylindrical beam of electrons, and means extending of said beam for varying the outsidediameter of said beam of .electrons in accordance with varying potentials applied to said means.

14. In apparatus of the character described, a ring shaped cathode, means for deriving and projecting therefrom a hollow, substantially cylinmeans extending in a direction substantially parallel to the axis of said beam for varying the outside diameter of said beainof electrons in accordance with varying potentials applied to said means.

15. In apparatus of the character described, a ring shaped cathode, means for deriving and projecting therefrom a hollow, substantially cylindrical beam of electrons, and means in the form of a helix located within and extending in a direction substantially parallel to the axis of said beam for varying the outside diameter of said beam of electrons in accordance with varying potentials applied to said means, said helix having varying potentials applied thereto.

16. In an electron discharge device, means for producing a hollow beam of electrons, a plurality of electrodes for alternately receiving said beam in accordance with variations in overall diameter of said beam, and a control electrode within said hollow beam and adapted to have varying potentials applied thereto for varying the diameter of said beam.

diameter thereof, positioned about 17. The method of operating an electron discharge device which comprises producing a hollow beam of electrons and varying the diameter of said beam in accordance with variations in signal waves applied to said device.

18. In an electrical discharge device, means for producing a stream of charged particles, a helical conductor adjacent said stream and in coupling relationship thereto and carrying an electric wave, the pitch of said helical conductor continually changing and being such that the velocity component of said wave parallel to said stream is substantially the same as the velocity of the charged particles in the stream.

19. In an electrical discharge device, means for producing a stream of electrons, a helical conductor adjacent said stream and in coupling relation thereto, a source of high frequency current coupled to one end of said helical conductor for producing an electromagnetic wave on said conductor, the pitch and diameter of said helical conductor having such values that the velocity component of the electromagnetic wave parallel to said stream is substantially the same as the velocity of the electrons in said stream, whereby the wave on said helical conductor produces cumulative effects on the electrons in said stream.

20. In an electron discharge device, means for producing a hollow beam of electrons, a helical conductor within said hollow beam and extending over a substantial portion of the length of said beam and carrying an electric wave, said helical conductor and beam being in coupling relation to each other, the pitch of said conductor changing over the length of the conductor and being such that the velocity component of said wave parallel to said beam is substantially the same as the velocity of the electrons in said beam.

21. In a multi-electrode electrical discharge device, means for producing a stream of charged particles, a helical conductor adjacent said stream and in coupling relation thereto and carrying an electric wave, said helical conductor having the same axis as said stream, means for supplying suitable polarizing potentials for the electrodes of said device, said device and helical conductor being so constructed and arranged that the velocity component of said wave parallel to said stream is substantially the same as the speed of propagation of the charged particles in said stream.

22. In an electrical discharge device, means at one end of said device for producing a concentrated stream of charged particles which travel substantially the length of said device, a helical conductor adjacent said stream and in coupling relation thereto, the axis of said helical conductor being parallel to or coincides with the axis of said stream, a target electrode near the other end of said device upon which said particles impinge, an input circuit comprising a source of high frequency waves coupled to that end of said helical conductor nearest said means, and an output circuit coupled to the other end of said helical conductor.

ANDREW V. HAEFF. 

